The efficiency of turbine is of paramount importance for cheaper power generation.
Two patents U.S. Pat. Nos. 5,211,703 (1993) and 5,192,190 (1993) on stationary blades are related to our field of invention.
The blades are considered to be most crucial apart from stationary flow path components for efficiency consideration. The improvement concerns to both stationary (guide and rotating moving) type of blades for axial steam turbines.
There are disadvantages associated with the present system of steam turbine blades.
The main disadvantage is that the turbine blades while converting heat energy into kinetic energy suffer two kinds of aerodynamic losses; one, the profile less due to streamwise boundary layer growth (along blade surfaces) and mixing in blade wakes, another due to secondary flow resulting from boundary layer growth along the hub and casing and flows resulting from turning of inlet boundary layer (passage vortex: pressure face to suction face in a cascade passage).
Steam turbine runner blades in high and intermediate pressure cylinders are of low height and low aspect; and most of the time one employs cylinder blades for energy transfer i.e. heat energy to kinetic energy.
Therefore the main object of the present invention of the improved cylindrical blades for axial steam turbines is to provide an improved blade profile for a wider stagger variation.
Another object of the present invention of improved cylindrical blades for axial steam turbines is to provide the blade suitable for a range of Mach numbers, incompressible to high subsonic flows.
According to the present invention there is provided improved cylindrical blades for axial steam turbines comprising a leading edge and a trailing edge and a pressure face and a suction face and an inlet flow angle and an outflow flow angle at the leading edge and trailing edge respectively characterized in that the blades formed by setting angle variation for incompressible flow as well as at subsonic Mach numbers at the exit with a lower loss for a range of stagger angles.
The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to the non-limiting exemplary embodiments of the invention represented in the accompanying drawings.